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        <li class="chapter " data-level="1.1" data-path="../../">
            
                <a href="../../">
            
                    
                    Introduction
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.2" data-path="../../architecture-overview/">
            
                <a href="../../architecture-overview/">
            
                    
                    Architecture Overview
            
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            <ul class="articles">
                
    
        <li class="chapter " data-level="1.2.1" data-path="../../architecture-overview/ddd-cqrs-concepts.html">
            
                <a href="../../architecture-overview/ddd-cqrs-concepts.html">
            
                    
                    DDD & CQRS Concepts
            
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        <li class="chapter " data-level="1.2.2" data-path="../../architecture-overview/event-sourcing.html">
            
                <a href="../../architecture-overview/event-sourcing.html">
            
                    
                    Event Sourcing
            
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        <li class="chapter " data-level="1.2.3" data-path="../../architecture-overview/event-driven-microservices.html">
            
                <a href="../../architecture-overview/event-driven-microservices.html">
            
                    
                    Event-Driven Microservices
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.3" data-path="../../axon-server-introduction.html">
            
                <a href="../../axon-server-introduction.html">
            
                    
                    Axon Server
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4" data-path="../../release-notes/">
            
                <a href="../../release-notes/">
            
                    
                    Release Notes
            
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        <li class="chapter " data-level="1.4.1" data-path="../../release-notes/rn-axon-framework/">
            
                <a href="../../release-notes/rn-axon-framework/">
            
                    
                    Axon Framework
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.4.1.1" data-path="../../release-notes/rn-axon-framework/rn-af-major-releases.html">
            
                <a href="../../release-notes/rn-axon-framework/rn-af-major-releases.html">
            
                    
                    Major Releases
            
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        <li class="chapter " data-level="1.4.1.2" data-path="../../release-notes/rn-axon-framework/rn-af-minor-releases.html">
            
                <a href="../../release-notes/rn-axon-framework/rn-af-minor-releases.html">
            
                    
                    Minor Releases
            
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            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.4.2" data-path="../../release-notes/rn-axon-server/">
            
                <a href="../../release-notes/rn-axon-server/">
            
                    
                    Axon Server
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.4.2.1" data-path="../../release-notes/rn-axon-server/rn-as-major-releases.html">
            
                <a href="../../release-notes/rn-axon-server/rn-as-major-releases.html">
            
                    
                    Major Releases
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.2.2" data-path="../../release-notes/rn-axon-server/rn-asse-minor-releases.html">
            
                <a href="../../release-notes/rn-axon-server/rn-asse-minor-releases.html">
            
                    
                    Minor Releases Standard Edition
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.2.3" data-path="../../release-notes/rn-axon-server/rn-as-minor-releases.html">
            
                <a href="../../release-notes/rn-axon-server/rn-as-minor-releases.html">
            
                    
                    Minor Releases Enterprise Edition
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.4.3" data-path="../../release-notes/axon-framework-extensions.html">
            
                <a href="../../release-notes/axon-framework-extensions.html">
            
                    
                    Axon Framework Extensions
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

    
        
        <li class="header">Getting Started</li>
        
        
    
        <li class="chapter " data-level="2.1" data-path="../../getting-started/quick-start.html">
            
                <a href="../../getting-started/quick-start.html">
            
                    
                    Quick Start
            
                </a>
            

            
        </li>
    

    
        
        <li class="header">Axon Framework</li>
        
        
    
        <li class="chapter " data-level="3.1" data-path="../../axon-framework/introduction.html">
            
                <a href="../../axon-framework/introduction.html">
            
                    
                    Introduction
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2" data-path="../../axon-framework/messaging-concepts/">
            
                <a href="../../axon-framework/messaging-concepts/">
            
                    
                    Messaging Concepts
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.2.1" data-path="../../axon-framework/messaging-concepts/anatomy-message.html">
            
                <a href="../../axon-framework/messaging-concepts/anatomy-message.html">
            
                    
                    Anatomy of a Message
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2.2" data-path="../../axon-framework/messaging-concepts/message-correlation.html">
            
                <a href="../../axon-framework/messaging-concepts/message-correlation.html">
            
                    
                    Message Correlation
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2.3" data-path="../../axon-framework/messaging-concepts/message-intercepting.html">
            
                <a href="../../axon-framework/messaging-concepts/message-intercepting.html">
            
                    
                    Message Intercepting
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2.4" data-path="../../axon-framework/messaging-concepts/supported-parameters-annotated-handlers.html">
            
                <a href="../../axon-framework/messaging-concepts/supported-parameters-annotated-handlers.html">
            
                    
                    Supported Parameters for Annotated Handlers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2.5" data-path="../../axon-framework/messaging-concepts/exception-handling.html">
            
                <a href="../../axon-framework/messaging-concepts/exception-handling.html">
            
                    
                    Exception Handling
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.2.6" data-path="../../axon-framework/messaging-concepts/unit-of-work.html">
            
                <a href="../../axon-framework/messaging-concepts/unit-of-work.html">
            
                    
                    Unit of Work
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.3" data-path="../../axon-framework/axon-framework-commands/">
            
                <a href="../../axon-framework/axon-framework-commands/">
            
                    
                    Commands
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.3.1" data-path="../../axon-framework/axon-framework-commands/modeling/">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/">
            
                    
                    Modeling
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.3.1.1" data-path="../../axon-framework/axon-framework-commands/modeling/aggregate.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/aggregate.html">
            
                    
                    Aggregate
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.1.2" data-path="../../axon-framework/axon-framework-commands/modeling/multi-entity-aggregates.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/multi-entity-aggregates.html">
            
                    
                    Multi-Entity Aggregates
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.1.3" data-path="../../axon-framework/axon-framework-commands/modeling/state-stored-aggregates.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/state-stored-aggregates.html">
            
                    
                    State Stored Aggregates
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.1.4" data-path="../../axon-framework/axon-framework-commands/modeling/aggregate-creation-from-another-aggregate.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/aggregate-creation-from-another-aggregate.html">
            
                    
                    Aggregate Creation from another Aggregate
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.1.5" data-path="../../axon-framework/axon-framework-commands/modeling/aggregate-polymorphism.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/aggregate-polymorphism.html">
            
                    
                    Aggregate Polymorphism
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.1.6" data-path="../../axon-framework/axon-framework-commands/modeling/conflict-resolution.html">
            
                <a href="../../axon-framework/axon-framework-commands/modeling/conflict-resolution.html">
            
                    
                    Conflict Resolution
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.3.2" data-path="../../axon-framework/axon-framework-commands/command-dispatchers.html">
            
                <a href="../../axon-framework/axon-framework-commands/command-dispatchers.html">
            
                    
                    Command Dispatchers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.3" data-path="../../axon-framework/axon-framework-commands/command-handlers.html">
            
                <a href="../../axon-framework/axon-framework-commands/command-handlers.html">
            
                    
                    Command Handlers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.4" data-path="../../axon-framework/axon-framework-commands/infrastructure.html">
            
                <a href="../../axon-framework/axon-framework-commands/infrastructure.html">
            
                    
                    Infrastructure
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.3.5" data-path="../../axon-framework/axon-framework-commands/configuration.html">
            
                <a href="../../axon-framework/axon-framework-commands/configuration.html">
            
                    
                    Configuration
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.4" data-path="../../axon-framework/events/">
            
                <a href="../../axon-framework/events/">
            
                    
                    Events
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.4.1" data-path="../../axon-framework/events/event-dispatchers.html">
            
                <a href="../../axon-framework/events/event-dispatchers.html">
            
                    
                    Event Dispatchers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.2" data-path="../../axon-framework/events/event-handlers.html">
            
                <a href="../../axon-framework/events/event-handlers.html">
            
                    
                    Event Handlers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.3" data-path="../../axon-framework/events/event-processors/">
            
                <a href="../../axon-framework/events/event-processors/">
            
                    
                    Event Processors
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.4.3.1" data-path="../../axon-framework/events/event-processors/subscribing.html">
            
                <a href="../../axon-framework/events/event-processors/subscribing.html">
            
                    
                    Subscribing Event Processors
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.3.2" data-path="../../axon-framework/events/event-processors/streaming.html">
            
                <a href="../../axon-framework/events/event-processors/streaming.html">
            
                    
                    Streaming Event Processors
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.4.4" data-path="../../axon-framework/events/event-bus-and-event-store.html">
            
                <a href="../../axon-framework/events/event-bus-and-event-store.html">
            
                    
                    Event Bus & Event Store
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.5" data-path="../../axon-framework/events/event-versioning.html">
            
                <a href="../../axon-framework/events/event-versioning.html">
            
                    
                    Event Versioning
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.4.6" data-path="../../axon-framework/events/event-serialization.html">
            
                <a href="../../axon-framework/events/event-serialization.html">
            
                    
                    Event Serialization
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.5" data-path="../../axon-framework/queries/">
            
                <a href="../../axon-framework/queries/">
            
                    
                    Queries
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.5.1" data-path="../../axon-framework/queries/query-processing.html">
            
                <a href="../../axon-framework/queries/query-processing.html">
            
                    
                    Query Processing
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.2" data-path="../../axon-framework/queries/query-dispatchers.html">
            
                <a href="../../axon-framework/queries/query-dispatchers.html">
            
                    
                    Query Dispatchers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.3" data-path="../../axon-framework/queries/query-handlers.html">
            
                <a href="../../axon-framework/queries/query-handlers.html">
            
                    
                    Query Handlers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.4" data-path="../../axon-framework/queries/implementations.html">
            
                <a href="../../axon-framework/queries/implementations.html">
            
                    
                    Implementations
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.5.5" data-path="../../axon-framework/queries/configuration.html">
            
                <a href="../../axon-framework/queries/configuration.html">
            
                    
                    Configuration
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.6" data-path="../../axon-framework/sagas/">
            
                <a href="../../axon-framework/sagas/">
            
                    
                    Sagas
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.6.1" data-path="../../axon-framework/sagas/implementation.html">
            
                <a href="../../axon-framework/sagas/implementation.html">
            
                    
                    Implementation
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.6.2" data-path="../../axon-framework/sagas/associations.html">
            
                <a href="../../axon-framework/sagas/associations.html">
            
                    
                    Associations
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.6.3" data-path="../../axon-framework/sagas/infrastructure.html">
            
                <a href="../../axon-framework/sagas/infrastructure.html">
            
                    
                    Infrastructure
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.7" data-path="../../axon-framework/deadlines/">
            
                <a href="../../axon-framework/deadlines/">
            
                    
                    Deadlines
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.7.1" data-path="../../axon-framework/deadlines/deadline-managers.html">
            
                <a href="../../axon-framework/deadlines/deadline-managers.html">
            
                    
                    Deadline Managers
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.7.2" data-path="../../axon-framework/deadlines/event-schedulers.html">
            
                <a href="../../axon-framework/deadlines/event-schedulers.html">
            
                    
                    Event Schedulers
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.8" data-path="../../axon-framework/testing/">
            
                <a href="../../axon-framework/testing/">
            
                    
                    Testing
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.8.1" data-path="../../axon-framework/testing/commands-events.html">
            
                <a href="../../axon-framework/testing/commands-events.html">
            
                    
                    Commands / Events
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.8.2" data-path="../../axon-framework/testing/sagas-1.html">
            
                <a href="../../axon-framework/testing/sagas-1.html">
            
                    
                    Sagas
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.9" data-path="../../axon-framework/tuning/">
            
                <a href="../../axon-framework/tuning/">
            
                    
                    Tuning
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="3.9.1" data-path="../../axon-framework/tuning/event-snapshots.html">
            
                <a href="../../axon-framework/tuning/event-snapshots.html">
            
                    
                    Event Snapshots
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.9.2" data-path="../../axon-framework/tuning/event-processing.html">
            
                <a href="../../axon-framework/tuning/event-processing.html">
            
                    
                    Event Processing
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.9.3" data-path="../../axon-framework/tuning/command-processing.html">
            
                <a href="../../axon-framework/tuning/command-processing.html">
            
                    
                    Command Processing
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="3.10" data-path="../../axon-framework/monitoring-and-metrics.html">
            
                <a href="../../axon-framework/monitoring-and-metrics.html">
            
                    
                    Monitoring and Metrics
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.11" data-path="../../axon-framework/spring-boot-integration.html">
            
                <a href="../../axon-framework/spring-boot-integration.html">
            
                    
                    Spring Boot Integration
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="3.12" data-path="../../axon-framework/modules.html">
            
                <a href="../../axon-framework/modules.html">
            
                    
                    Modules
            
                </a>
            

            
        </li>
    

    
        
        <li class="header">Axon Server</li>
        
        
    
        <li class="chapter " data-level="4.1" data-path="../../axon-server/introduction.html">
            
                <a href="../../axon-server/introduction.html">
            
                    
                    Introduction
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.2" data-path="../../axon-server/installation/">
            
                <a href="../../axon-server/installation/">
            
                    
                    Installation
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.2.1" data-path="../../axon-server/installation/local-installation/">
            
                <a href="../../axon-server/installation/local-installation/">
            
                    
                    Local Installation
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.2.1.1" data-path="../../axon-server/installation/local-installation/axon-server-se.html">
            
                <a href="../../axon-server/installation/local-installation/axon-server-se.html">
            
                    
                    Axon Server SE
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.2.1.2" data-path="../../axon-server/installation/local-installation/axon-server-ee.html">
            
                <a href="../../axon-server/installation/local-installation/axon-server-ee.html">
            
                    
                    Axon Server EE
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="4.2.2" data-path="../../axon-server/installation/docker-k8s/">
            
                <a href="../../axon-server/installation/docker-k8s/">
            
                    
                    Docker / K8s
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.2.2.1" data-path="../../axon-server/installation/docker-k8s/axon-server-se.html">
            
                <a href="../../axon-server/installation/docker-k8s/axon-server-se.html">
            
                    
                    Axon Server SE
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="4.2.2.2" data-path="../../axon-server/installation/docker-k8s/axon-server-ee.html">
            
                <a href="../../axon-server/installation/docker-k8s/axon-server-ee.html">
            
                    
                    Axon Server EE
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="4.3" data-path="../../axon-server/administration/">
            
                <a href="../../axon-server/administration/">
            
                    
                    Administration
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.3.1" data-path="../../axon-server/administration/admin-configuration/">
            
                <a href="../../axon-server/administration/admin-configuration/">
            
                    
                    Configuration
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="4.3.1.1" data-path="../../axon-server/administration/admin-configuration/configuration.html">
            
                <a href="../../axon-server/administration/admin-configuration/configuration.html">
            
                    
                    System Properties
            
                </a>
            

            
        </li>
    
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                                <h1 id="handler-enhancers">Handler Enhancers</h1>
<p>Handler Enhancers allow you to wrap handlers and add custom logic to the execution, or eligibility of handlers for a certain message. This differs from <code>HandlerInterceptor</code>s in that you have access to the aggregate member at the time of resolving, and it allows for more fine-grained control. You can use handler enhancers to intercept and perform checks on groups of <code>@CommandHandler</code>s or <code>@EventHandler</code>s.</p>
<p>To create a handler enhancer you start by implementing <code>HandlerEnhancerDefinition</code> and overriding the <code>wrapHandler()</code> method. All this method does is give you access to the <code>MessageHandlingMember&lt;T&gt;</code> which is an object representing any handler that is specified in the system.</p>
<p>You can then sort these handlers based on their annotations by using the <code>annotationAttributes(Annotation annotation)</code> method. This will filter out only those handlers that use that <code>Annotation</code>.</p>
<p>For your handler enhancer to run you&apos;ll need to either create a <code>META-INF/services/org.axonframework.messaging.annotation.HandlerEnhancerDefinition</code> file containing the fully qualified class name of the handler enhancer you have created, or register it explicitly in the Configurer.</p>
<p>Example of a Handler Enhancer that filters messages based on an expected Meta-Data key and value.</p>
<pre><code class="lang-java"><span class="hljs-comment">// 1</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ExampleHandlerDefinition</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">HandlerEnhancerDefinition</span> </span>{ 

    <span class="hljs-meta">@Override</span> <span class="hljs-comment">// 2</span>
    <span class="hljs-keyword">public</span> &lt;T&gt; <span class="hljs-function">MessageHandlingMember&lt;T&gt; <span class="hljs-title">wrapHandler</span><span class="hljs-params">(MessageHandlingMember&lt;T&gt; original)</span> </span>{
        <span class="hljs-keyword">return</span> original.annotationAttributes(MyAnnotation.class) <span class="hljs-comment">// 3</span>
                .map(attr -&gt; (MessageHandlingMember&lt;T&gt;) 
                             <span class="hljs-keyword">new</span> ExampleMessageHandlingMember&lt;&gt;(original, attr))
                .orElse(original); <span class="hljs-comment">// 5</span>
    }

    <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ExampleMessageHandlingMember</span>&lt;<span class="hljs-title">T</span>&gt; 
                             <span class="hljs-keyword">extends</span> <span class="hljs-title">WrappedMessageHandlingMember</span>&lt;<span class="hljs-title">T</span>&gt;</span>{

        <span class="hljs-keyword">private</span> <span class="hljs-keyword">final</span> String metaDataKey;
        <span class="hljs-keyword">private</span> <span class="hljs-keyword">final</span> String expectedValue;

        <span class="hljs-function"><span class="hljs-keyword">private</span> <span class="hljs-title">ExampleMessageHandlingMember</span><span class="hljs-params">(
                             MessageHandlingMember&lt;T&gt; delegate,
                             Map&lt;String, Object&gt; annotationAttributes)</span> </span>{
            <span class="hljs-keyword">super</span>(delegate);
            metaDataKey = (String) annotationAttributes.get(<span class="hljs-string">&quot;metaDataKey&quot;</span>);
            expectedValue = (String) annotationAttributes.get(<span class="hljs-string">&quot;expectedValue&quot;</span>);
        }

        <span class="hljs-meta">@Override</span>
        <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">boolean</span> <span class="hljs-title">canHandle</span><span class="hljs-params">(Message&lt;?&gt; message)</span> </span>{
            <span class="hljs-keyword">return</span> <span class="hljs-keyword">super</span>.canHandle(message) &amp;&amp; expectedValue.equals(message.getMetaData().get(metaDataKey)); <span class="hljs-comment">// 4</span>
        }
    }
}
</code></pre>
<ol>
<li>Implement the <code>HandlerEnhancerDefinition</code> interface</li>
<li>Override the <code>wrapHandler</code> method to perform your own logic.</li>
<li>Sort out the types of handlers you want to wrap, for example any handlers with a <code>MyAnnotation</code>.</li>
<li>Handle the method inside of a <code>MessageHandlingMember</code>, in this case, indicating the handler is only suitable if the meta-data key matches a value.</li>
<li>If you are not interested in wrapping the handler, just return the original that was passed into the <code>wrapHandler</code> method.</li>
</ol>
<p>It is possible to configure <code>HandlerDefinition</code> with Axon <code>Configuration</code>. If you are using Spring Boot defining <code>HandlerDefintion</code>s and <code>HandlerEnhancerDefinition</code>s as beans is sufficient (Axon autoconfiguration will pick them up and configure within Axon <code>Configuration</code>).</p>
<p> tabs 
 tab title=&quot;Axon Configuration API&quot; </p>
<pre><code class="lang-java">Configurer configurer = DefaultConfigurer.defaultConfiguration();
configurer.registerHandlerDefinition((c, clazz) -&gt;
                                             MultiHandlerDefinition.ordered(
                                                     MultiHandlerEnhancerDefinition.ordered(
                                                             ClasspathHandlerEnhancerDefinition.forClass(clazz),
                                                             <span class="hljs-keyword">new</span> MyCustomEnhancerDefinition()
                                                     ),
                                                     <span class="hljs-keyword">new</span> MyCustomHandlerDefinition(),
                                                     ClasspathHandlerDefinition.forClass(clazz)
                                             ));
</code></pre>
<p> endtab </p>
<p> tab title=&quot;Spring Boot AutoConfiguration&quot; </p>
<pre><code class="lang-java"><span class="hljs-comment">// somewhere in configuration</span>
<span class="hljs-comment">// for a HandlerDefinition</span>
<span class="hljs-meta">@Bean</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> HandlerDefinition <span class="hljs-title">myCustomHandlerDefinition</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> CustomHandlerDefinition(); 
}

<span class="hljs-comment">// or to define a handler enhancer</span>
<span class="hljs-meta">@Bean</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> HandlerEnhancerDefinition <span class="hljs-title">myCustomHandlerEnhancerDefinition</span><span class="hljs-params">()</span> </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> MyCustomEnhancerDefinition(); 
}
</code></pre>
<p> endtab 
 endtabs </p>

                                
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